1. Field of the Invention
The invention relates to a strain of Geotrichum candidum for use in the biological control of postharvest rots on fruit, particularly citrus.
2. Description of Related Art
Damage to fruit caused by fungal post-harvest diseases results in significant economic losses to the fruit and citrus industry worldwide. Included among some of the more destructive post-harvest pathogens or molds affecting citrus are Penicillium digitatum, Geotrichum candidum (Link ex Pers), and Penicillium italicum. Conventional techniques for control of these pathogens have relied upon the application of fungicides after harvest or prior to shipping. However, the extensive use of fungicides has been the subject of increasing public concern as posing potential hazards to human health and the environment. Moreover, fungicides are often ineffective with the development of fungicide-resistant strains of the pathogens.
To illustrate the scope of the problem, green mold of citrus, caused by P. digitatum, is the major postharvest disease of citrus in south Texas, and is one of the two diseases responsible for the majority of decay losses in the California and Arizona citrus industries (the other being blue mold, caused by P. italicum). TBZ and imazalil are the fungicides currently used for control of green mold in these regions. However, due to very low residue tolerances for TBZ in Europe, TBZ may not be used on fruit used for juice destined for that market. Moreover, the effectiveness of TBZ against green mold is not optimal. Therefore, green mold on citrus remains a serious problem, even on citrus treated with TBZ.
Recently, techniques involving the postharvest treatment of fruits with antagonistic microorganisms have been developed which have shown promise for the control of postharvest pathogens. For example, Pusey et al. (1986, Plant Dis., 86:753-756) controlled brown rot in peaches, caused by Monilinia fructicola, with the bacterium Bacillus subtilis. Roberts (U.S. Pat. No. 5,244,680) disclosed strains of Cryptococcus effective for the control of postharvest rots, as well as a method for selecting bacteria and yeasts effective as biocontrol agents. Wilson et al. (U.S. Pat. No. 5,425,941) also isolated strains of Candida oleophila effective for controlling a number of different postharvest diseases on fruit.